An aircraft gas turbine engine includes a main combustor for generating combustion gases for propelling an aircraft in flight. Military gas turbine engines typically also include an augmenter or afterburner which is a secondary combustor at the aft end of the engine for providing additional thrust when desired. In the main combustor as well as the augmenter, fuel is typically channeled thereto through a plurality of circumferentially spaced apart fuel injectors or spraybars which receive metered fuel from common manifolds circumferentially surrounding the combustors.
In the augmenter, for example, the circumferentially spaced apart fuel injectors include those ranging in elevation from the bottom of the engine to the top which therefore introduces pressure variations in the fuel channeled thereto due to gravity which is typically referred to as differences in hydraulic pressure head. Fuel at the bottom of the engine has a higher pressure head which therefore will result in an uneven fuel distribution circumferentially around the engine unless suitable distribution valves are provided. Various fuel distribution assemblies are known in the art for accommodating the differential pressure head, which assemblies vary in complexity, space requirements, and weight all of which are significant factors in the design of an aircraft engine. The common manifold typically provides fuel through pigtail fuel lines to individual distribution valves typically mounted to an outer casing of the engine, with respective fuel injectors being mounted to the valves. The combustor environment such as that found in an augmenter is relatively hot which typically requires expensive high temperature materials and suitable cooling provisions for ensuring an effective life of the fuel distribution assembly.
These fuel systems, therefore, typically require a substantial number of parts which must be accurately manufactured and joined together in spite of manufacturing stackup tolerances. Since the valves are subjected to relatively high temperatures, the typical springs found therein are subject to high temperature spring relaxation which can shift the flow controlling effect of the valve unless suitably compensated for.